Paulino was acquired from the Colorado Rockies for cash considerations. Tejeda was designated for assignment. Both are right-handers.
Tejeda, 29, was in his fourth season with the Royals and had just come off the disabled list after missing more than a month because of shoulder problems. He has an 0-1 record and a 6.14 ERA in nine games.
Ironically, Tejeda was praised by manager Ned Yost after pitching an inning against Baltimore in Wednesday night's loss. He gave up a home run, but his fastball velocity had jumped back up to about 94 mph.
"I felt like he was really starting to come around, but these other kids have out-pitched him and it was just one of those situations where we needed a spot on the 25-man roster," Yost said. "Robby's real close to getting back, but still, in the pecking order, he was down a little from all the rest of those guys."
Paulino, 27, was 0-4 with a 7.36 ERA in 18 relief outings this season for the Rockies before he was designated for assignment last Sunday. He'll join the Royals for Friday night's game in Texas.
He's pitched in parts of four Major League seasons, including 2007, 2009 and 2010 for the Houston Astros. His career record is 6-25 with a 5.93 ERA in 65 games, including 34 starts. He has 201 strikeouts and 97 walks in 223 innings.
"Our scouts say he's really got good stuff. We'll just have to see when he gets here," Yost said. "Our people like him a lot and say he's got a chance to be a starter down the road. We'll use him in the 'pen long right now; it just gives us more options."
The success of the Royals' rookie-dominated bullpen made the decision on Tejeda one of necessity, in Yost's view. It made it very difficult to send one of them to the Minors to clear room for Paulino, he said.
"None of the decisions are going to be easy," Yost said. "They're all going to be tough decisions because all these kids are throwing so well. That's been the strength of our team."
Paulino, from the Dominican Republic, originally was signed by the Astros as a shortstop in 2001. He began pitching in 2003. The Rockies acquired him last winter in exchange for infielder Clint Barmes.
Tejeda started the season as the primary setup man for closer Joakim Soria, but he struggled early in the season and went on the disabled list April 14 with shoulder inflammation. The Royals claimed him on waivers from the Rangers during the 2008 season.
In his four Kansas City seasons, Tejeda had a 9-10 record and 3.57 ERA in 123 games, including seven starts. He racked up 186 strikeouts against 98 walks in 181 1/3 innings.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.